In the lithographic processes usually applied in the production of such devices, it is the general goal to achieve ever smaller structures. That is, the critical dimensions (CD) have to become smaller to allow a higher integration of the semiconductor devices.
The problem is that optical and other physical or chemical limitations of a current process generation do not allow the production of structure beyond a certain threshold. Currently deep ultra violet (DUV) light lithography with wavelengths of 248 nm or 198 nm is under development. The limit for CD using this technology seems to be a critical dimension of about 60 nm.